Electrodeposition of nickel



1 United States Patent 3,152,975 ELECTRQDEPOSET 6N 0F NICKEL OttoKardos, Red Bank, and William B. Stoddard, Jr.,

Matawan, Nl, assignors to Hanson-Van Winkle- Munning Company, acorporation of New Jersey No Drawing. Filed Feb. 7, 1961, Ser. No.87,551 11 Claims. (Cl. 204-49) This invention relates toelectroplatingand, more particularly, to electrodepositing nickel from an aqueousacidic nickel plating bath. The invention is based on the discovery thatthe isomeric vinylbenzenesulfonic acids and certain of their salts, whenincorporated in a nickel plating bath. Particularly in conjunction withvarious other additives, are remarkably effective for promoting theformation of ductile electroplates which are much smoother than thebasis metal plated in such a bath.

This ability of an electroplating bath to improve on the smoothness ofthe basis metal is known as leveling ability and can be usedindustrially to reduce or eliminate mechanical or electrochemicalfinishing of the base metal.

We have found that in all instances the use of one of the isomericvinylbenzenesulfonic acids or their corresponding alkali metal,ammonium, magnesium or nickel salts in a nickel plating bath exerts apronounced leveling effect on the electroplate formed during the platingoperation. Accordingly, the invention provides an improved process forproducing a nickel deposit substantially smoother than the basis metalto which it is applied which comprises electrodepositing nickel from anaqueous acidic solution of at least one nickel salt in which there isdissolved a substituted-styrene having a structure represented by theformula V r in which M is a cation substituent of the group consistingof hydrogen, alkali metals, ammonium, magnesium and nickel. Although anyof the three isomeric vinylbenzenesulfonic acids may be used in a nickelplating bath in accordance with the invention, particularly satisfactoryresults have been obtained using the sodium salt of para isomer,p-vinylbenzenesulfonic acid.

By themselves, the isomeric vinylbenzenesulfonic acids and their salts,and in particular p-vinylbenzenesulphonic acid, are capable of promotingthe formation of excellent bright nickel electrodeposits over thecurrent density range of less than 10 to more than 100 amperes persquare foot and of exerting a considerable leveling effect on the bath.When, however, a small quantity of p-vinylbenzenesulfonic acid or one ofits above-mentioned salts is incorporated in the plating bath togetherwith either a Class I sulfo-oxygen carrier brightener or a Class 11secondary brightening compound, the brightness capacity of the bath isextended and the electrodeposit is bright over a very wide currentdensity range with little diminution in the leveling effect exerted bythis substituted-styrene on the bath.

Only relatively small quantities of p-vinylbenzenesulfonic acid or itssalts are required in the plating bath, especially when used inconjunction with a Class I sulfooxygen carrier brightener or a Class IIsecondary brightener, for we have found that the p-vinylbenzenesulfonicacid and its salts exert a noticeable leveling efiect on the bath atconcentrations as low as abdut 0.1 gram per liter. There appears to beno critical upper limit on the concentration of thissubstituted-styrene, but there is no particular advantage in using morethan about 20 grams per liter, or even less. At concentrations over therange from about 0.1 to about 20 grams per liter, the level effect ofp-vinylbenzenesulfonic acid (or its salts) in nickel plating baths hasbeen found to be especially pro- 3,152,975 Patented Oct. 13, 1964 "icenounced when the bath is operated at temperatures rangmg from about C.to about 85 C. and at a pH from 3.0 to 5.0, with or without agitation ofthe bath.

The compounds listed in Table I are examples of the sulfo-oxygencompounds which, when used in combination with p-vinylbenzenesulfonicacid and its above-mentioned salts promote the formation of bright andductile nickel deposits which are substantially smoother than the basemetal to which they are applied. These sulfo-oxygen compounds may beused over a wide range of concentrations A to 80 grams per liter), butpreferably are used in an amount in the range from about 1 to about 20grams per liter.

TABLE I Organic Sulfa-Oxygen Compounds (1) Unsaturated aliphaticsulfonic acids, and alkali metal, ammonium, magnesium, and nickel saltsthereof:

Sodium vinyl sulfonate, H C=CHSO Na Sodium allyl sulfonate, H C=CHCH SONa (2) Mononuclear aromatic sulfonic acids, and alkali metal, ammomum,magnesium, and nickel salts thereof:

Benzene monosulfonic acid, C H SO H Sodium benzene monosultonate, C H SONa Nickel benzene monosulfonate, (C l-l SO Ni Sodium p-toluenemonosulfonate, CI-l C H SO Na p-Chlorobenzene sulfonic acid, ClC H SOl-l 'Sodium p-chlorobenzene sulfonate, ClC H SO Na Sodium p-bromobenzenesulfonate, BrC -H SO Na 1,2-dichlorobenzene sulfonic acid, Cl C H SO l-l1,2- or 2,5-dichlorobenzene sulfonates, sodium salt,

Cl C H SO Na v m-Benzene disulfonic acid, C H (SO H) Sodium m-benzenedisulfonate, C H (SO Na) Nickel m-benzene disulfonate, C H (SO Nio-Sulfobenzoic acid monoamrnonium salt,

H0OCC H SO NH lamino-2,5-benzene disulfonic acid, H NC H (SO H)o-Aminobenzene sulfonic acid, H NC H SO H (3) Mononuclear aromaticsulfinic acids, and alkali metal, ammonium, magnesium, and nickel saltsthereof:

Sodium benzene sulfinate, C H SO Na Sodium p-toluene sulfinate, CH C HSO Na (4) Mononuclear aromatic sulfonamides and sulfonimides:

Benzene sulfonamide, C H SO NH p-Toluene sulfonamide, CH C H SO NHo-Sulfobenzoic imide,

CGHlCONI'ISOg Benzyl sulfonamide, C l-l CI-l SO NH Benzenesulfhydroxamic acid, C H SO NHOH NJJ-dimethyLp-toluene sulfonamidc,

CH C H SO N CH 2 N,N-dicarboxyethyl benzene sulfonamide,

C6H5SO'2N 2 (5) Binuclear aromatic sulfonic acids, and akali metal,ammonium, magnesium, and nickel salts thereof:

3 Sodium Z-naphthol-3,6-disulfonate, HOC H (SO Na)1-naphthylamine-3,6,8-trisulfonic acid,

(6) Heterocyclic sulfonic acids, and alkali metal, ammonium, magnesium,and nickel salts thereof: Thiophene sulfonic acid, C H S-SO' H Sodiumthiophene sulfonate, C H S-SO Na For the most part, only free sulfonicacids are listed in Table I. However, the alkali metal, ammonium,magnesium, and nickel salts are in all cases the full equivalent of theacids, and may be used in their place in carrying out the process ofthis invention.

Even brighter electrodeposits are obtained when p-vinylbenzenesulfonicacid (or its salts) is employed in the plating bath in conjunction witha Water-soluble acetylenic compound, particularly the oxygen-containingacetylenic compounds. For example, plating baths which contain sodiump-vinylbenzenesulfonate together with a water-soluble acetylenicbrightener additive have a much wider brightening capacity and moreoften yield bright electrodeposits than baths which contain eitheradditive alone. Our experiments indicate that any water-solubleacetylenic compound effectively cooperates to some degree withp-vinylbenzenesulfonic acid or its salts in enhancing the leveling anduniformity of brightness of the nickel electroplate, though someacetylenic compounds are more effective than others.

The common structural feature of these water-soluble acetyleniccompounds is the preesnce of a highly nucleophilic triple bond which isneither sterically hindered nor impeded in approaching the cathode. Onlyrelatively small quantities of the acetylenic compounds are required inthe bath when used in conjunction with p-vinylbenzenesulfonic acid orany of its above-mentioned salts. Concentrations as low as 0.1 millimolper liter, or even less, are effective in some cases, though in generalit is preferable to employ at least 1 rnillimol per liter. In general,there is no advantage in employing more than about 25 millimols perliter of the acetylenic brighteners, and in most plating baths the fullbenefit of their presence is achieved with concentrations in the rangefrom 1 to millimols per liter.

in which each of R and R are substituents of the group consisting ofhydrogen, alkyl, alkenyl, alkynyl, and hydroxy-substituted andalkoxy-substituted alkyl, alkenyl, and alkynyl groups, R is asubstituent of the group consisting of hydrogen, halogen, alkyl,alkenyl, alkynyl, hydroxy-substituted and alkoxy-substituted alkenyl andalkynyl groups, and substituted-alkyl groups having the structuralconfiguration in which each of R and R are substituents of the groupconsisting of hydrogen, alkyl, alkenyl, alkynyl, and hydroxy-substitutedand alkoxy-substituted alkyl, alkenyl, and alkynyl groups, and each of Rand R, are substituents of the group consisting of hydroxy, alkoxy,carboxysubstituted alkoxy, formoxy, alkanoxy, halogen and polyoxygroups. Where R is a substituted-alkyl group having theabove-illustrated structural configuration, then the acetylenic compoundis termed an a, x'-disubstituted acetylenic compound, since both carbonatoms vicinal to the same acetylenic bond contain either the same or adiiferent functional group. The compounds listed in Table II areexamples of various tit-substituted acetylenic compounds which may beused successfully in plating baths containing p-vinylbenzenesulfonicacid or one of its salts. As indicated previously, these acetyleniccompounds are preferably used in concentrations from about 1 to about 25millimols per liter.

TABLE II a-Substituted Acetylenic Compounds l z Ra O E 0- 9-31 CompoundR1 Ra R: R

2-Butyne-lA-diol -H H CHzOH 0H 1,4-Di-(fl-hydroxyethoxy)-2-butyne H CH OCH; CHzOH O CHzCHzO H 1,4-Diacetoxy-2-butyne H 0 Hi 0 lOI 0 H3 0 (I? CH;

3-Butyne-1,2-dio1 CH2OH -H H O H B-Methyl-l-butyne- CHa OH3 H -OH3-Methyl-l-pentyn-3-ol. CzH5 CH -11 OH 2-Propyn-l-ol E I -H H OH2,5-Dimethyl-1-oeten-3-yn-5-ol C3H GH; (3113 --OH 3-Methyl-l-nonyn-3-olCH13 OH; H OH 2,4-Hexadiyne-l,6-diol H CECCH:O H OH 1Methoxy-2-propyne HH 0 CH3 3-Methoxy-3-methyl-4,6-heptadiyne O 1115 CH -GECH O 0 H3-Ethoxy-3,5,7-trimethyll-octyne... O H CH H O CzHu 1-Formoxy-2-propyneH H '-H 0 $311 1-Acet0xy-2-propyne -11 -H H O C CH33-Methy1-1-nonyn-3-yl acetate -0 H1a -CH3 H O (H CH3 Among the mostsatisfactory acetylenic brightening agents are those prepared byreacting either an a-liydroxy or an a,a-dihydroxy acetylenic compound,such as those listed in Table H, with either ethylene oxide orepichiorohydrin. These adducts readily dissolve in acidic nickel platingbaths and are unusually effective in such baths both in promoting theformation of bright and ductile electrodeposits over wide currentdensity ranges and in exerting a pronounced leveling effect on the bathduring the plating operation. Two such adducts which are notablyeffective when used in conjunction with p-vinylbenzenesulfonic acid orany of its above-mentioned salts,

particularly with sodium p-vinylbenzenesulfonate, are thea,ot-di-(polyoxy)-2-butynes obtained upon the reaction of 12-butyne-l,4-diol with ethylene oxide and with epichlorohydrin.

2-butyne-l,4-diol reacts with ethylene oxide in the presence of a baseto form a l,4-di-(hydroxypolyethoxy)- Z-butyne which is structuralcharacterized by the formula II brighteners as unsaturated N-oxides(e.g., pyridine N-oxide); aromatic phosphinic acids (e.g.,phenylphosphinic acid); wamino-N-heterocyclic compounds (e.g., a-aminopyridines and oz-pyrimidines); bis-pyridyls (e.g.,

2,2'-dipyridyl); olefinic alcohols (e.g., 2-bu'tene-1,4-diol);,

the condensation products of tetraethylene-pentamine with acryonitrile,methyl sulfate, epichlorohydrin, benzenesulfonyl chloride, ordimethylchloracetal; pyridinium halides (e.g., ethylene-bis-pyridiniumbromide, dimethylene-bis- 41.25 grams per liter of boric acid. Afteradjusting the pH of the bath to 4.5 with sulfuric acid, the,electrodeposits were formed in an open vessel on roughened steelcathodes, using vigorous air agitation, a bath temperature of 60 C., andan average current density of 60 amperes per square foot. In several ofthese examples, the ditference in roughness values of the electroplatedand the unplated (roughened) steel panels was measured to determinewhether the additive or combination of additives employed exerted aleveling effect onrthe bath during the plating operation.

EXAMPLE I Using a nickel plating solution having the basic compositiondescribed above and to which had been added 0.5 gram per liter of sodiump-vinylbenzenesulfonate, nickel was electrodeposited on a roughenedsteel panel over a period of 30 minutes. Under these conditions, theresultant electrodeposit was uniformly bright. The difierence betweenroughness values between the electroplated and unplated (roughened)steel panel was 86 per: cent, indicating that sodiump-vinyl-benzenesulfonate (which exists as the free acid in the solution)exerted a pronounced leveling eflect on the bath during the platingoperation.

- EXAMPLE II a To the basic Watts plating solution described above wasadded 0.5 gram per li-ter'of sodium p-vinylbenzenesulfonate and 0.1 gramper liter of 2-butyne-l,4-diol, and nickel was electrodeposited on aroughened steel panel,

' using conditions which were identical to those described pyridiniumchloride, and nitropyridinium pyrazole chloride); various azo compounds,such as mono, di-, and riarninoazo-benzenes; halogenated carbonyls, suchas chloral hydrate, bromal hydrate, and butylchloral hydrate; coumarincompounds; alkylated quinolinium halides (egi, benzyl methyl quinoliniumchloride); polyalkylene amines; and amino polyaryl methanes.

The following examples are illustrative of the effectiveness with whichp-vinylbenzenesulfonic acid and its abovementioned salts may be used innickel electroplating baths in accordance with the invention. In each ofthese examples, the basic plating bath employed was an aqueous solutioncontaining 300 grams per liter of nickel sulfate, 45 grams per liter ofnickel chloride (hexahydrate), and

in Example I. The resultant electrodeposit was brilliant in appearance,the increase in the brilliance of the deposit produced by the additionof 2-butyne-1,4-diol to the bath being easily discernable.

i EXAMPLE III Nickel was electrodeposited under the same conditions asthose employed in Example II, with the sole difference being that 0.1gram per liter of sodium 1,4-dihydroxy-2- 'butene-2-sulfonate (thereaction product of equimolar quantities of 2-butyne-l,4-diol and sodiumbisulfite) was also added to the bath. The resultant electrodeposit wasbrilliant in appearance and substantially smoother than the roughenedsteel panel to which it was applied, and was not alfected when the bathwas contaminated with copper and Zinc impurities. When 2 grams per literof sodium fluoborate was added to this bath, the electrodeposit remainedunaffected even when the bath was contaminated with iron. 7

EXAMPLE IV Using the basing plating bath having thecomposition 3 givenabove and to which had been added 4 grams per i liter of sodiumbenzenesulfonate, nickel was electrode-' posited on a roughened steelpanel for a period of 30 minutes at a bath temperature of 60 C. and acurrent density of 60 amperes per square foot. There was no dilferenceUpon the addition of 1.2 grams per liter ofsodium pvinylbenzenesulfonate to this bath, the leveling effect 7 exerted by thebath was increased to 65 percent, the resultant electrodeposit beinguniformly bright in appearance.

The general principle illustrated in each of the foregoing examples,that p-vinylbenzenesulfonic acid exerts a pronounced leveling effect onnickel plating baths when used alone or in combination with variousother additives, was repeatedly and consistently verified in many testsusing a large number of Class I carrier brighteners or Class IIsecondary brighteners.

Although the examples have illustrated the use of sodiump-vinylbenzenesulfonate in the standard Watts nickel electroplatingbath, which is prepared by dissolving nickel sulfate, nickel chloride,and boric acid in water, similar advantages are also attained whenp-vinylbenzenesulfonic acid or its above-mentioned salts are dissolvedin other types of aqueous acidic nickel electroplating baths. Forexample, p-vinylbenzenesulfonic acid and its salts are beneficial whenused in straight nickel sulfate baths, in straight nickel chloridebaths, and in various other m'ckel plating baths based on using nickelformate, nickel sulfamate, or nickel fluoroborate as the nickel saltwhich is dissolved in an aqueous acidic solvent, or in nickel platingbaths containing cobalt salts. Consequently, the invention is applicableto electrodeposition from any aqueous acidic solution of one or morenickel salts.

We claim:

1. A process for producing a nickel deposit substantially smoother thanthe basis metal to which it is applied which compriseselectrodepos-iting nickel from an aqueous acidic solution of at leastone nickel salt in which there is dissolved from about 0.1 to aboutgrams per liter of a substituted-styrene having a structure representedby the formula in which M is a cation substituent of the groupconsisting of hydrogen, alkali metals, ammonium, magnesium, and

nickel. A

2. A process for producing a nickel deposit substantially smoother thanthe basis metal to which it is applied which comprises electrodepositingnickel from an aqueous acidic solution of at least one nickel salt inwhich there is dissolved from about 0.1 to about 20 grams per liter of asubstituted-styrene of the group consisting of p-vinylbenzenesulfonicacid and the alkali metal, magnesium, ammonium, and nickel saltsthereof.

3. A process for producing a nickel deposit substantially smoother thanthe basis metal to which it is applied which comprises electrodepositingnickel from an aqueous acidic solution of at least one nickel salt inwhich there is dissolved from about 0.1 to about 20 grams per liter of asubstituted-styrene of the group consisting of pvinylbenzenesulfonicacid and the alkali metal, magnesium, ammonium, and nickel saltsthereof, and from about /1 to about 80 grams per liter of awater-soluble sulfooxygen compound of the group consisting ofunsaturated aliphatic sulfonic acids, mononuclear and binuclear aromaticsulfonic acids, mononuclear aromatic sulfinic acids, the alkali metal,magnesium, ammonium, and nickel salts of said acids, and mononucleararomatic sulfonamides and sulfonirnides.

4. A process for producing a nickel deposit substantially smoother thanthe basis metal to which it is applied which comprises electrodepositingnickel from an aqueous acidic solution of at least one nickel salt inwhich there is dissolved from about 0.1 to about 20 grams per liter of asubstituted-styrene of the group consisting of p-vinylbenzenesulfonicacid and the alkali metal, magnesium, ammonium, and nickel saltsthereof, and from about 0.1 to about millimols per liter of awater-soluble acetylenic compound.

lenic compound having a structure represented by the formula R2 R CEC-(3-R1 in which each of R and R are substituents of the group consistingof hydrogen, alkyl, alkenyl, alkynyl, and hydroxy-substituted andalkoxy-substituted alkyl, alkenyl, and alkynyl groups, R is asubstituent of the group consisting of hydrogen, halogen, alkyl,aikenyl, alkynyl, hydroxy-substituted and alkoxy-substituted alkenyl andalkynyl groups, and substituted-alkyl groups having the structuralconfiguration in which each of R and R are substituents of the groupconsisting of hydrogen, alkyl, alkenyl, alkynyl, and hydroxy-substitutedand alkoxy-substituted alkyl, alkenyl, and alkynyl groups, and each ofR, and R, are substituents of the group consisting of hydroxy, alkoxy,carboxy-substituted alkoxy, formoxy, alkanoxy, halogen and polyoxygroups.

6. A process for producing a nickel deposit substantially smoother thanthe basis metal to which it is applied which comprises electrodepositingnickel from an aqueous acidic solution of at least one nickel salt inwhich there is dissolved from about 0.1 to about 20 grams per liter of asubstituted-styrene of the group consisting of p-vinylbenzenesulfonicacid and the alkali metal, magnesium, ammonium, and nickel saltsthereof, and from about 0.1 to about 3 grams per liter of2-butyne-1,4-diol.

7. A process for producing a nickel deposit substantially smoother thanthe basis metal to which it is applied which comprises electrodepositingnickel from an aqueous acidic solution of at least one nickel salt inwhich there is dissolved from about 0.1 to about 20 grams per liter of asubstituted-styrene of the group consisting of p-vinylbenzenesulfonicacid and the alkali metal, magnesium, ammonium, and nickel saltsthereof, and from about 0.1 to about 3 grams per liter of a1,4-di-(hydroxyethylpolyethoxy)-2-butyne having the structural formula.p-vinylbenzenesulfonic acid and the alkali metal, magnesium, ammonium,and nickel salts thereof, and from about 0.01 to about 2 grams per literof a bisulfite addition product having a structure represented by theformula in which M is a cation substituent of the group consisting ofhydrogen, alkali metals, ammonium, magnesium, and

nickel. 7

'9. A process for producing a nickel deposit substan tially smootherthan the basis metal to which it is applied which compriseselectrodeposi-ting nickel from an aqueous acidic solution of at leastone nickel salt in which there is dissolved from about 0.1 to about 20grams per liter of a substituted-styreneof the group consisting ofp-vinylbenzenesulfonic acid and the alkali metals, magnesium, ammonium,and nickel salts thereof, from about A to about 80 grams per liter of awater-soluble sulfooxygen compound of the group consisting ofunsaturated aliphatic sulfonic acids, mononuclear and binuclear aromaticsulfonic acids, mononuclear aromatic sulfinic acids, the alkali metal,magnesium, ammonium, and nickel salts of said acids, and mononucleararomatic sulfonamides and sulfonimides, and from about 0.1 to about 25millimols per liter of a water-soluble acetylenic compound.

10. A process for producing a nickel deposit substantially smoother thanthe basis metal to which it is applied which comprises electrodepositingnickel from an aqueous acidic solution of at least one nickel salt inwhich there is dissolved from about :1 to about 20 grams per liter of asubstituted-styrene of the group consisting of p-vinylbenzenesulfonicacid and the alkali metal, magnesium, ammonium, and nickel saltsthereof, from about A to about 80 grams per liter of a water-solublesulfooxygen compound of the group consisting of unsaturated aliphaticsulfonic acids, mononuclear and binuclear aromatic sulfonic acids,mononuclear aromatic sulfinic acids, the alkali metal, magnesium,ammonium, and nickel salts of said acids, and mononuclear aromatic,sulfonamides and sulfonimides, from about 0.1 to about 25 millimols perliter of a water-soluble acetylenic compound, and from about 0.01 toabout 2 grams per liter of a bisulfite addition product having astructure represented by the formula HOOHPCH=C CHQOH in which M is acation substituent of the group consisting of hydrogen, alkali metals,ammonium, magnesium, and nickel.

11. In the process of electroplating nickel from an acid aqueoussolution of a nickel salt, the step comprising adding to said solutionat least about 0.5 gram per liter of a compound selected from the groupconsisting of para vinyl benzene sulfonic acid and salts thereof.

References Cited in the file of this patent UNITED STATES PATENTS2,455,555 Brown Dec. 7, 1948 2,466,677 Brown Apr. 12, 1949 2,523,190Brown Sept. 19, 1950 2,712,522 Kardos et al. July 5, 1955 FOREIGNPATENTS 1,141,135 France Mar. 11, 1957 1,231,332 France Apr. 11, 1960UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3l52,975 October 13 1964 Otto Kardos et a1.

It is hereby certified that error-appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 1, line l4 for "bath, Particularly" read bath particularly line45 for "p-vinylbenzenesulphonic" read p-vinylbenzenesulfonic line 7O for"level" read leveling column 3, line 29 for "preesnce" read presencecolumn 5 line 35, for "structural" read structurally column 6, line 67,for "basing" read basic column 7, line 24 for "fluoroborate" readfluoborate Signed and sealed this 30th day of March 1965c (SEAL) Attest:

ERNEST W. SWIDER I EDWARD J. BRENNER Attcsting Officer Commissioner ofPatents

1. A PROCESS FOR PRODUCING A NICKEL DEPOSIT SUBSTANTIALLY SMOOTHER THANTHE BASIS METAL TO WHICH IT IS APPLIED WHICH COMPRISES ELECTRODEPOSITINGNICKEL FROM AN AQUEOUS ACIDIC SOLUTION OF AT LEAST ONE NICKEL SALT INWHICH THERE OF A SUBSTITUTED-STYRENE HAVING A STRUCTURE REPRESENTED BYTHE FORMULA